Field Due to a Long Wire: the Figure Shows Four

Field due to a long wire: The figure shows four different sets of insulated wires that cross each other at right angles without actually making electrical contact. The magnitude of the current is the same in all the wires, and the directions of current flow are as indicated. For which (if any) configuration will the magnetic field at the center of the square formed by the wires be equal to zero?

A) A
B) B
C) C
D) D
E) The field is not equal to zero in any of these cases.